Dental appliance and mouthguard formed of polyolefin elastomer

ABSTRACT

A self-customizable dental appliance adapted to lie within the mouth of a person including occlusal pads with a connecting arch or a u-shaped style base with upstanding labial and lingual walls. The appliance is formed of a semi-crystalline polyolefin polymer or crystallizable blend. In one embodiment, the appliance is formed of elastomeric propylene-ethylene polypropylene, optionally including high density polypropylene. An optional occlusal lifting pad can be used in the self-customizable dental appliance.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/571,325 filed May 14, 2004 the entirety of which ishereby incorporated by reference into this application and U.S.Provisional Patent Application No. 60/579,539 filed Jun. 14, 2004 theentirety of which is also hereby incorporated by reference into thisapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to athletic mouthguards and dentalappliances, and specifically to self-customizable mouthguards and dentalappliances.

2. Description of Related Art

It is known that mouthguards have been used to protect athletes incontact sports from injury to the teeth and also to protect thetemporomandibular joint from destructive forces. Recent evidence alsoindicates that mouthguards may be beneficial in minimizing or preventingconcussion. Performance of mouthguards is described in Elkin, M.,Increased Athletic Performance using Mouthguards—True or False?, J. NewJersey Dental Assoc., 1996; Stenger, J. M., Mouthguards protectionagainst shock to the head, neck and teeth, J. Am. Dental Assoc., 1964;Duda, M., Which Athletes Should Wear Mouthguards?, Phys. and SportsMed., 1987; and Hickey, J. C., The Relation of mouth protectors tocranial pressure and deformation, J. Am. Dental Assoc., 1967.

Athletes tend to clench their teeth upon exertion. This clenchingcreates considerable forces on the upper and lower jaws and can lead todamage to the teeth, headaches, neck pain and injury to thetemporomandibular joint. Therefore, dental appliances and/or mouthguardshave been created to place pads between the upper and lower dentition toprevent this clenching and possible damage to the teeth and otherstructures.

Historically, mouthguards have been made of ethylene vinyl acetate(EVA). Due to the user clenching and chewing on the appliance, it issubject to degradation. EVA is translucent or white and cannot be madeclear. EVA also has a mild ester-like odor and will degrade to hazardousvinyl acetate, acetic acid, carbon monoxide and hazardous hydrocarbonoxidation products. While the mechanical and physical properties of EVAgenerally fulfill the safety requirements for a custom fittedmouthguard, attempts to mass-produce EVA as a Boil-and-Bite,“do-it-yourself” mouthguard have had limited success and acceptance (seeBishop, B. M., Davis, E. H., von Fraunhoffer, J. A., “Materials formouth protectors” J. Prosthet. Dent. 1985; 53:256-61 and Chalmers, D.J., “Mouthguards: Protection for mouth in the rugby union” Sports Med.1998; 25(5):339-49; Winters, Sr., J. E. “Role of properly fittedmouthguards in prevention of sport-related Concussion” J. AthleticTraining 2001; 36(3): 339-341). These mouthguards do not fit well andtheir poor retention plus their lack of proper extension into the buccalvestibule have led Park et al. to state unless dramatic improvements aremade, they should not be promoted to customers as they are now (seePark, J. B., Shaull, K. L., Overton, B., Donly, K. I., “Improvingmouthguard” J. Prosthe.t Dent. 1994; 72: 373-80.

Currently, commercially available mouthguards are (arbitrarily)classified as:

-   -   1. Stock over-the-counter—one size fits all. They must be held        in place by clenching the teeth together—an obvious        contraindication for continuous, vigorous sports requiring        unobstructed airways.    -   2. Boil-and-Bite, mouth formed—these are placed in boiling water        and then fitted into the mouth. When athletes attempt to fit        these mouthguards, the resulting fit is often inadequate, loose        and uncomfortable (see American Society for Testing and        Materials. Standard practice for care and use of mouthguards (F        687-80). Reapproved 1992. Philadelphia (PA): American Society        for Testing and Materials, 1992).

Attempts been made in engineering EVA for a better fit, comfort andprotection; these include sophisticated multilayer composites with adifferent softening temperature, custom gel fit liner, grip fittechnology, or blending EVA with various polymers such as Kraton andpolyurethane. (See Kittelsen et al., “Quadruple composite performanceenhancing mouthguard (U.S. Pat. No. 6,675,807); Wagner, E. C. “Customfit mouthguard” (U.S. Pat. No. 5,566,684); Gel Max Shock Doctor'sMouthguard. www.shockdoc.com; Shock Doctor's 7001 V3.0 Mouthguard.www.shockdoc.com; Shock Doctor's V3 Mouthguard. www.shockdoc.com); andBrett et al., “Mouthguard and method of making” U.S. Pat. No.6,584,978.). Despite these efforts, comfortable custom fittedmouthguards are still difficult to achieve and many athletic trainersand sports participants still prefer the custom-fabricated mouthguards,i.e. from dentist made study casts of the teeth. They are comfortable,fit better with good retention, and allow the user to breathe and speakmore easily. Despite the cost, experts in the medical, dental and sportsprofessions are still recommending the custom fitted mouthguard as thebest choice and protection (see Chalmers, D. J., “Mouthguards:Protection for mouth in the rugby union” Sports Med. 1998; 25(5):339-49;Winters, Sr., J. E. “Role of properly fitted mouthguards in preventionof sport-related Concussion” J. Athletic Training 2001; 36(3): 339-341).

FIG. 1 illustrates a conventional noncustom mouthguard 10 whichgenerally includes a horseshoe or u-shaped base or occlusal pad 11 witha lingual wall 12 and a labial wall 13.

U.S. Pat. No. 6,491,036 discloses a low density polyethylene dentalappliance and mouthguard including a nucleating agent. A suitablematerial is EXACT® from ExxonMobil Chemical Company of Houston, Tex.77253-3272. This material has ethylene crystallinity which produces anon-elastomeric material with little flexibility or no shrinkage.

There is a need for mouthguards and dental appliances of custom fitwithout the need to have it formed by a dentist. There is a need forself-customizing dental appliance or mouthguard which is aesthetic,offers protection for the teeth, exhibiting strong tensile strength,high impact properties, flexibility, and have little or no odor.

SUMMARY OF THE INVENTION

The present invention relates to a self-customizable dental appliancecomprised of polyolefin-based thermoplastic elastomer. The dentalappliance is securely adapted and fitted to the teeth for absorbingforces upon contact with the dental appliance. The dental appliance canhave a horseshoe or u-shaped base with an occlusal pad and upstandinglabial and lingual walls. A channel between the walls accommodates theteeth of a user. Optionally, the appliance can include a high densitymaterial. The use of a high-density material increases the crystallinetemperature so that the self-customizable appliance will harden fasterfor a customized fit.

The self-customizable dental appliance of the present invention exhibitsstrong tensile strength, high impact properties, flexibility, and haslittle or no odor. The self-customizable appliance of the presentinvention can be made clear or colored for identification. Theself-customizable appliance of the present invention is nonhazardous.The self-customizable appliance of the present invention can be easilymolded by the user of the dental appliance. The self-customizable dentalappliance has the advantages of (a) giving the user ample time, (forexample, 2 to 3 minutes) to properly fit the mouthguard at a workabletemperature below 60° C., during which the material must remain soft andelastic/extensible to conform the contour of the mouth and teeth; (b)providing shrink without any distortion once the mouthguard iscomfortably in place; and (c) possessing a good balance of hardness,soft feel and shock absorbing power.

The invention will be more fully described by reference to the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art mouthguard made of anelastomer and not designed for a custom fit.

FIG. 2 is a bottom plan view of the self-customizable dental appliance,mouthguard or splint placed on the upper teeth.

FIG. 3 is a perspective view of the custom fit dental appliance,mouthguard or splint which has been formed to fit the shape of the teethand gums which has been formed with occlusal posterior pads and aconnective arch.

FIG. 4 is a perspective view of a custom fit dental appliance,mouthguard or splint including a channel for teeth.

FIG. 5 is a perspective view of a custom fit dental appliance,mouthguard or splint including a channel for teeth including a fit lockappliance.

FIG. 6 is a perspective view of a custom fit dental appliance,mouthguard or splint including a tether.

FIG. 7 is a perspective view of an anterior spacer and handle.

FIG. 8 is a perspective view of a dental appliance of a bleaching trayincluding a liner.

FIG. 9 is a perspective view of a dental appliance of an upperimpression tray.

FIG. 10 is a perspective view of a dental appliance of a lowerimpression tray.

DETAILED DESCRIPTION

Reference will now be made in greater detail to a preferred embodimentof the invention, an example of which is illustrated in the accompanyingdrawings. Wherever possible, the same reference numerals will be usedthroughout the drawings and the description to refer to the same or likeparts.

FIGS. 2 through 4 illustrate dental appliance 20 in accordance with theteachings of the present invention. Dental appliance 20 can be formed asa mouthguard or dental splint. Dental appliance 20 is formed of base 22.Lingual wall 24 and buccal wall 25 extend from base 22. Channel 26 isformed between lingual wall 24 and buccal wall 25. Channel 26 has awidth W, which is less than width W₂ of teeth 28. For example, channel26 can have a width in the range of about 1 mm to about 12 mm.

Dental appliance 20 can include a layer of material to form occlusallifting pad 30. Occlusal lifting pad 30 can have a height in the rangeof about 3 mm to about 4 mm. Occlusal lifting pad 30 is positionedbetween the maxilla and mandible adjacent to molars and/or bicuspids foropening the bite of a user.

Dental appliance 20 is formed of a material which is self-customizableby a user of dental appliance 20. Dental appliance 20 can be formed of asemi-crystalline polyolefin polymer or polymer blend. Suitablepolyolefin polymers include propylene-ethylene copolymer. Thesemi-crystalline polymer can be a thermoplastic polymer. Thesemi-crystalline polyolefin polymer can have low density. Suitablepolymers for forming dental appliance 20 can include low densitypolypropylene. Optionally, a high density polypropylene can be used withthe low density polyolefin.

Suitable polyolefin polymers include propylene-ethylene copolymersproduced in the presence of a metallocene catalyst and activator asdescribed in U.S. Pat. No. 6,525,157 hereby incorporated by referenceinto this application. The copolymer can comprise about 5 to 25% byweight of ethylene-derived units and about 55 to 75% by weight ofpropylene derived units.

Suitable thermoplastic polymer blends comprise a composition formed ofan isotatic polypropylene component and an alpha olefin and propylenecopolymer, the copolymer comprising crystallizable alpha olefinsequences as described in U.S. Pat. No. 6,635,715 and U.S. Pat. No.6,642,316 hereby each incorporated by reference into this application.The composition can be formed by blending at least a first polymercomponent and a second polymer component, the blend comprising: fromabout 2% to about 95% by weight of the first polymer component, thefirst polymer component comprising isotactic polypropylene and having amelting point greater than about 110° C., and copolymerizing propyleneand ethylene using a chiral metallocene catalyst system, the copolymerhaving crystallinity from about 2% to about 65% from isotacticpolypropylene sequences, a propylene content of from about 75% to about90% by weight, a melting point of from 50° C. to 105° C., and wherein aglass transition temperature of the second polymer component is retainedin the polymer blend. Alternatively, the polymer blend can be anuncrosslinked blend composition comprising a dispersed phase of acrystalline polymer component in a continuous phase of a crystallizablepolymer component wherein: a) the crystalline polymer component isdispersed in phases less than 3 μm×3 μm×100 μm in size, b) the blendcomposition has greater than 65% propylene units by weight, c) the blendcomprises greater than 1% but less than 40% by weight is based on thetotal weight of the blend of a crystalline first polymer component andless than 99% but greater than 60% by weight based on the total weightof the blend of a crystallizable second polymer component, suchcrystallinity being due to stereoregular polymerized propylene units, d)both first and second polymer component contain stereoregularpolymerized propylene units of identical tacticity, e) the blend has atensile elongation greater than 650%, wherein the first polymercomponent is a propylene homopolymer and has a melting point by DSCequal to or above 115° C., and the second polymer component is acopolymer of the propylene units and from about 8% to about 25% byweight ethylene units and has a melting point equal to or less thanabout 100° C.

A suitable material is Vistamaxx from ExxonMobil Chemical Company ofHouston, Tex. 77253-3272.

Other polymers can be blended or laminated with the propylene-ethylenecopolymer to provide enhanced properties. For example, suitable polymerscan include elastomers, plastomers, and rubber.

Colorants can be added to the propylene-ethylene copolymer to achieve asuitable aesthetic appearance. For example, the colorants can be clear.A suitable colorant is sold by Milliken Chemical under the tradedesignation CLEARTINT® (Milliken Chemical Division of Milliken & Company(Spartanburg, S.C.)). Light reflective material can also be added orattached to the propylene-ethylene copolymer to achieve additionalaesthetic appearance.

A method forming a self-customizable dental appliance comprises thesteps of placing the dental appliance 20 in a hot medium. For example,after molding into dental appliance 20, the user simply places dentalappliance 20 into a hot liquid, for example, dental appliance 20 can beplaced into water having a temperature of about 60° C. to about 100° C.for a few seconds. The appliance is then removed and self-customized tothe user's mouth, teeth and gums to provide a custom fit. Alternatively,dental appliance 20 can be placed in a wet paper towel and heated in amicrowave oven. For example, dental appliance 20 can be heated for about30 seconds to about 90 seconds in a microwave oven on a high setting. Inone example, dental appliance 20 can be heated for about 60 seconds in amicrowave on a high setting. Dental appliance 20 can be cooled for ashort period of time, for example about 5 seconds. After placing dentalappliance 20 in the mouth for customizing, dental appliance 20 can beleft in the mouth until comfortable or placed in cold water for twominutes and returned to the mouth.

Dental appliance 20 can have a height of H, which is substantially theheight of teeth 28, and after molding, dental appliance can be retainedagainst teeth 28 due to the self-customizable fit.

In one embodiment, dental appliance 20 can be used as temporomandibularjoint (TMJ) bruxism appliance, as shown in FIG. 4.

In an embodiment, fit lock 40 is positioned over dental appliance 20after placement of dental appliance 20 in the user's mouth, as shown inFIG. 5. Fit lock 40 holds and locks dental appliance 20 in theself-customizable shape during cooling of dental appliance 20. Fit lock40 can have a slightly larger dimension to fit over dental appliance 20.For example, fit lock 40 can be formed of plastic.

In an embodiment of the present invention, tether 50 is attached todental appliance 20, as shown in FIG. 6. For instance, tether 50 canextend from front 36 of dental appliance 20. Tether 50 can be used forremoving dental appliance 20 from the hot medium or a microwave oven. Inone embodiment, tether 50 of dental appliance 20 can be used to attachto a face mask of a helmet. Alternatively, tether 50 can be removed fromdental appliance 20 before use.

In an alternate embodiment, handle 52 can be coupled to front 36 ofdental appliance 20. Anterior spacer 54 can be coupled to bottom portion55 of handle 52. Anterior spacer 54 can have a height of about 3 mm toabout 4 mm.

In an alternate embodiment, dental appliance 20 can be used as ableaching tray, as shown in FIG. 8. Dental appliance 20 includes liner60. Liner 60 can be used for absorption of a bleaching material 62.

In an alternate embodiment, dental appliance 20 is formed as an upperimpression tray, as shown in FIG. 9. Dental appliance 20 comprises fullpalatal pad 70 and buccal wall 25. Handle 74 extends from front 36 ofdental appliance 20.

In an alternate embodiment, dental appliance 20 is formed as a lowerimpression tray, as shown in FIG. 10. Lower impression tray comprisesbuccal wall 25 and occlusal lifting pad 30. The upper impression trayand lower impression tray can be used for taking impressions.

Dental appliance 20 has improved shrinkage to product a custom fit incomparison with EVA mouthguards. Dental appliance 20 has increasedoverall fitting time in comparison with EVA mouthguards.

The following Example is illustrative of the present invention asdescribed in the claims which follow thereafter:

EXAMPLE

Dental appliance 20 was made from a thermoplastic polyolefin elastomerreferred to as Vistamaxx™ which is manufactured by ExxonMobil Chemical.Table 1 compares the physical and mechanical property range of Vistamaxxwith a mouthguard formed of EVA 28% vinyl acetate. The results show thatthe physical and mechanical properties match or surpass EVA. Dentalappliance 20 provides a greater rate of crystallization or fitting time,i.e., the time interval before the material stiffens at bodytemperature. EVA hardens within 10 to 20 seconds. Any attempt to fit themouthguard within this time interval results in an ill-fitted mouthguardwith poor retention. Dental appliance 20 takes 2 to 3 minutes for themouthguard to harden. This gives the user ample time to properly fit themouthguard. During this time interval, the material remains soft andextensible. In addition, the high shrinkage of dental appliance 20allows the mouthguard to shrink, giving a snug fit with excellentretention to the teeth and jaw within 5 minutes. TABLE I Physical andMechanical Dental Conventional Mouthguard Properties Appliance 20 EVA(28% Vinyl acetate) Density, g/cc 0.86-0.89 0.95 Melting Point° C. 55-160 70 Tensile Strength (psi) 2200-4500 2100 Die C Tear Strength(ibf/in) 130-330 250 Elongation at Break (%)  100-1500 800 FlexuralModulus (psi)) 1500-6500 2300 Hardness (Shore A) 50-90 80 Shrinkage toteeth Excellent Poor Overall fitting time 2-3 minutes 10-20 seconds

It is to be understood that the foregoing description and specificembodiments are merely illustrative of the best mode of the inventionand the principles thereof. Various modifications and additions may bemade to the present invention by those skilled in the art withoutdeparting from the spirit and scope of this invention which is to belimited only by the scope of the appended claims.

1. A self-customizable dental appliance comprising one or more channelsand an upstanding wall extending from said one or more channels beingformed of a semi-crystalline polyolefin polymer or a crystallizablepolymer blend, wherein said dental appliance is adapted to securely fitto teeth.
 2. The self-customizable dental appliance of claim 1 whereinsaid polyolefin polymer is a thermoplastic elastomer.
 3. Theself-customizable dental appliance of claim 1 wherein said polyolefinpolymer is low density polypropylene.
 4. The self-customizable dentalappliance of claim 1 further comprising a high density polyolefinpolymer.
 5. The self-customizable dental appliance of claim 4 whereinsaid high density polyolefin polymer is high density polypropylene. 6.The self-customizable dental appliance of claim 1 wherein saidpolyolefin polymer is propylene-ethylene copolymer.
 7. Theself-customizable dental appliance of claim 1 wherein said polymer blendis formed by blending at least a first polymer component and a secondpolymer component, the blend comprising: from about 2% to about 95% byweight of the first polymer component, the first polymer componentcomprising isotactic polypropylene and having a melting point greaterthan about 110° C., and copolymerizing propylene and ethylene using achiral metallocene catalyst system, the copolymer having crystallinityfrom about 2% to about 65% from isotactic polypropylene sequences, apropylene content of from about 75% to about 90% by weight, a meltingpoint of from 50° C. to 105° C., and wherein a glass transitiontemperature of the second polymer component is retained in the polymerblend.
 8. The self-customizable dental appliance of claim 1 wherein thecrystallizable polymer blend is crystallizable alpha olefin andpropylene copolymer.
 9. The self-customizable dental appliance of claim1 further comprising a layer of material extending upwardly in height,wherein said layer of material is adapted to be positioned adjacent tomolars and/or bicuspids.
 10. The self-customizable dental appliance ofclaim 1 wherein the crystallizable polymer blend is a dispersed phase ofa crystalline polymer component in a continuous phase of acrystallizable polymer component wherein: a) the crystalline polymercomponent is dispersed in phases less than 3 μm×3 μm×100 μm in size, b)the blend composition has greater than 65% propylene units by weight, c)the blend comprises greater than 1% but less than 40% by weight is basedon the total weight of the blend of a crystalline first polymercomponent and less than 99% but greater than 60% by weight based on thetotal weight of the blend of a crystallizable second polymer component,such crystallinity being due to stereoregular polymerized propyleneunits, d) both first and second polymer component contain stereoregularpolymerized propylene units of identical tacticity, e) the blend has atensile elongation greater than 650%, wherein the first polymercomponent is a propylene homopolymer and has a melting point by DSCequal to or above 115° C., and the second polymer component is acopolymer of the propylene units and from about 8% to about 25% byweight ethylene units and has a melting point equal to or less thanabout 100° C.
 11. The self-customizable dental appliance of claim 10wherein said layer of material has a height in the range of about 3 mmto about 4 mm.
 12. The self-customizable dental appliance of claim 1further comprising: a colorant added to said semi-crystalline polyolefinpolymer or crystallizable polymer or blend.
 13. The self-customizabledental appliance of claim 12 wherein the colorant is clear.
 14. Theself-customizable dental appliance of claim 1 further comprising: alight reflective material added to said semi-crystalline polyolefinpolymer or crystallizable polymer or blend.
 15. The self-customizabledental appliance of claim 1 further comprising a fit lock appliance,said fit lock appliance fitting over said upstanding wall and said oneor more channels of said dental appliance during molding of said dentalappliance, said fit lock having a slightly larger dimension than saiddental appliance.
 16. The self-customizable dental appliance of claim 15wherein said fit lock is formed of plastic.
 17. The self-customizabledental appliance of claim 1 further comprising a handle extending from afront of said dental appliance.
 18. The self-customizable dentalappliance of claim 16 further comprising an anterior spacer extendingfrom a bottom portion of said handle.
 19. The self-customizable dentalappliance of claim 1 wherein said dental appliance is a mouthguard. 20.The self-customizable dental appliance of claim 1 wherein said dentalappliance is a dental splint.
 21. The self-customizable dental applianceof claim 1 wherein said dental appliance is a temporomandibular jointbruxism appliance.
 22. The self-customizable dental appliance of claim 1wherein said dental appliance is a bleaching appliance.
 23. Theself-customizable dental appliance of claim 1 further comprising a linerfor receiving a bleaching composition.
 24. The self-customizable dentalappliance of claim 1 wherein the dental appliance is an upper impressiontray including a full palatal.
 25. The self-customizable dentalappliance of claim 1 wherein the dental appliance is a lower impressiontray.
 26. A method for forming a self-customizable dental appliancecomprising the steps of: molding said dental appliance, said dentalappliance comprising one or more channels and an upstanding wallextending from said one or more channels being formed of asemi-crystalline polyolefin polymer or a crystallizable polymer blend;placing said molded dental appliance in a liquid having a temperature inthe range of about 60° C. to about 100° C.; and placing said heatedmolded dental appliance in the mouth of a user for providing a customfit of said dental appliance to teeth and gums of the user.
 27. A methodfor forming a self-customizable dental appliance comprising the stepsof: molding said dental appliance, said dental appliance comprising oneor more channels and an upstanding wall extending from said one or morechannels being formed of a semi-crystalline polyolefin polymer or acrystallizable polymer blend; heating said molded dental appliance in amicrowave; and placing said heated molded dental appliance in the mouthof a user for providing a custom fit of said dental appliance to teethand gums of the user.
 28. The method of claim 27 wherein said microwaveheats said dental appliance for about 30 seconds to about 90 seconds ona high power setting.